This work will identify and characterize the inorganic mineral phase of dentin and enamel in certain animal models, including rat, mouse, and embryonic calf; will trace the temporal changes in the chemical and physical nature of the mineral phase from its initial deposition to its most mature state in these two tissues; and will determine the spatial and structual relationships between the inorganic solid phase and the organic elements and components in odontoblasts and ameloblasts and in their adjacent extracellular tissue spaces. The proposal will principally involve the use of transmission and scanning electron microscopy, electron an x-ray diffraction, electron probe x-ray microanalysis, and infrared spectroscopy. Techniques for specimen preparation will include conventional, aqueous methods as well as anhydrous procedures for maintaining the location and distribution of calcium phosphate comprising the mineral phase of the tissues.